Channel access and medium reservation mechanism

ABSTRACT

This disclosure provides systems, methods and apparatuses for coordinating access to a shared wireless medium among multiple master devices operating on the same frequency band. In some implementations, master devices may contend for access to the shared medium during a medium reservation window (MRW). During the MRW, master devices may advertise their intent to reserve at least a portion of the shared medium for one or more timeslots within a subsequent medium utilization period. The reservation messages may be broadcast to other master devices in the vicinity to prevent other master devices from accessing the wireless medium during a reserved timeslot. In some implementations, the owner of a timeslot may share at least a portion of its timeslot with other master devices. For example, the timeslot owner may enable other master devices to utilize an unused portion of the wireless medium, such as unused channels, spatial streams, or time.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority to U.S. Provisional PatentApplication No. 62/530,011 entitled “CHANNEL ACCESS AND MEDIUMRESERVATION MECHANISM” filed on Jul. 7, 2017 and assigned to theassignee hereof. The disclosure of the prior Application is consideredpart of and is incorporated by reference in this patent application.

TECHNICAL FIELD

This disclosure relates to wireless networks, and specifically tomanaging channel access to a shared wireless medium.

DESCRIPTION OF THE RELATED TECHNOLOGY

A wireless local area network (WLAN) may be formed by one or more accesspoints (APs) that provide a shared wireless communication medium for useby a number of client devices or stations (STAs). Each AP, which maycorrespond to a Basic Service Set (BSS), periodically broadcasts beaconframes to enable any STAs within wireless range of the AP to establishand maintain a communication link with the WLAN. In a typical BSS, onlyone device (such as a STA or an AP) may access the wireless medium atany given time, and a STA may be associated with only one AP at a time.WLANs that operate in accordance with the IEEE 802.11 family ofstandards are commonly referred to as Wi-Fi networks.

To prevent collisions in the WLAN, only one wireless device (such as anAP or a STA) may access the wireless medium at a time. In a typicalWLAN, wireless devices may compete for access to the wirelesscommunication medium. For example, the devices may use carrier sensemultiple access collision avoidance (CSMA/CA) techniques to “listen” tothe wireless medium to determine when the wireless medium is idle. Whenthe wireless medium has been idle for a given duration, the devices maycontend for medium access (such as by waiting a “back-off” period beforeattempting to transmit on the wireless medium). The winning device maybe granted exclusive access to the shared wireless medium for a periodof time commonly referred to as a transmit opportunity (TXOP), duringwhich only the winning device may transmit (or receive) data over theshared wireless medium.

Although CSMA/CA techniques may be useful for preventing collisionswithin a single BSS environment, the crowding of frequency bands mayrequire individual APs to coordinate access to the wireless medium withother “master devices” (such as APs or cellular base stations) operatingin the same frequency band. For example, the 6 GHz frequency band may beshared by Wi-Fi and other wireless communication technologies (includingvarious cellular communication technologies). Thus, there is a need tocoordinate channel access among master devices in a shared wirelessmedium.

SUMMARY

The systems, methods and devices of this disclosure each have severalinnovative aspects, no single one of which is solely responsible for thedesirable attributes disclosed herein.

One innovative aspect of the subject matter of this disclosure can beimplemented in a method of sharing a wireless medium among multiplemaster devices. The method may be performed by a master device, and mayinclude steps of contending with other master device for access to awireless medium during a first medium reservation window (MRW); upongaining access to the wireless medium during the first MRW, transmittinga message to the other master devices advertising a reservation of thewireless medium for a timeslot within a first medium utilization period(MUP); and servicing one or more client devices over the wireless mediumduring the reserved timeslot within the first MUP. In some aspects, eachof the wireless device may comprise a wireless access point or acellular base station.

In some implementations, the method may further include steps ofdetermining an availability of the wireless medium based on reservationmessages transmitted by the other master devices during the first MRW;and selecting the timeslot based on the availability of the wirelessmedium. The reservation may be for a number of channels, a number ofspatial dimensions, a duration of time, or any combination thereof.

In some implementations, at least one of the first MRW or the first MUPmay have a fixed duration. In some other implementations, the method mayfurther include a step of determining a duration of the first MRW basedat least in part on a number of master devices contending for access tothe shared wireless medium during the first MRW. Still further, in someimplementations, the method may further include a step of determining aduration of the first MUP based at least in part on a medium accessrequirement of each master device that reserves a timeslot within thefirst MUP.

In some implementations, the method may further include a step ofsharing at least a portion of the wireless medium, during the reservedtimeslot, with another master device. The shared portion of the wirelessmedium may include a number of unused channels, a number of unusedspatial dimensions, an unused duration of time, or a combinationthereof. In some aspects, the step of sharing at least a portion of thewireless medium may include a step of advertising an availability of theshared portion of the wireless medium at the start of the reservedtimeslot. In some other aspects, the step of sharing at least a portionof the wireless medium may include a step of advertising an availabilityof the shared portion of the wireless medium after servicing the one ormore client devices.

In some implementations, the master device and the other master devicemay belong to the same master device cluster. Thus, in some aspects, themethod may further include steps of determining, during a second MRW,that the other master device has reserved the wireless medium for atimeslot within a second MUP; refraining from contending for access tothe wireless medium during the second MRW upon determining that theother master device has reserved the wireless medium; and coordinatingaccess to the wireless medium with the other master device during thetimeslot reserved by the other master device within the second MUP.

Another innovative aspect of the subject matter described in thisdisclosure can be implemented in a master device (such as a wirelessaccess point or a cellular base station). The master device includes oneor more processors and a memory. The memory stores instructions that,when executed by the one or more processors, cause the master device tocontend with other master devices for access to a wireless medium duringa first medium reservation window (MRW); upon gaining access to thewireless medium during the first MRW, transmit a message to the othermaster devices advertising a reservation of the wireless medium for atimeslot within a first medium utilization period (MUP); and service oneor more client devices over the wireless medium during the reservedtimeslot within the first MUP.

In some implementations, execution of the instructions may further causethe master device to determine an availability of the wireless mediumbased on reservation messages transmitted by the other master devicesduring the first MRW; and select the timeslot based on the availabilityof the wireless medium. The reservation may be for a number of channels,a number of spatial dimensions, a duration of time, or any combinationthereof.

In some implementations, at least one of the first MRW or the first MUPmay have a fixed duration. In some other implementations, execution ofthe instructions may further cause the master device to determine aduration of the first MRW based at least in part on a number of masterdevices contending for access to the wireless medium during the firstMRW. In some other implementations, execution of the instructions mayfurther cause the master device to determine a duration of the first MUPbased at least in part on a medium access requirement of each masterdevice that reserves a timeslot within the first MUP.

In some implementations, execution of the instructions may further causethe master device to share at least a portion of the wireless medium,during the reserved timeslot, with another master device. The sharedportion of the wireless medium may include a number of unused channels,a number of unused spatial dimensions, an unused duration of time, or acombination thereof.

In some implementations, the master device and the other master devicemay belong to the same master device cluster. Thus, in some aspects,execution of the instructions may further cause the master device todetermine, during a second MRW, that the other master device hasreserved the wireless medium for a timeslot within a second MUP; refrainfrom contending for access to the wireless medium during the second MRWupon determining that the other master device has reserved the wirelessmedium; and coordinate access to the wireless medium with the othermaster device during the timeslot reserved by the other master devicewithin the second MUP.

Another innovative aspect of the subject matter described in thisdisclosure can be implemented in a method of accessing a shared wirelessmedium by a client device. The method may include steps of detecting areservation message transmitted by a master device during a mediumreservation window (MRW); determining, based on the reservation message,a timeslot for which the master device has reserved access to a sharedwireless medium within a medium utilization period (MUP); and schedulingcommunications with the master device over the shared wireless mediumbased at least in part on the timeslot reserved by the master device.

In some implementations, the step of detecting the reservation messagemay include a step of scanning a subset of channels allocated for theMRW, wherein the subset of channels is less than a number of channelsavailable on the shared wireless medium. In some implementations, thestep of scheduling communications with the master device may includesteps of communicating with the master device over the shared wirelessmedium during the timeslot reserved by the master device; and operatingin a power save state during the remainder of the MUP.

In some aspects, the reservation message may include informationindicating one or more capabilities of the master device. In someimplementations, the method may further include a step of associatingwith the master device based at least in part on the informationincluded in the reservation message.

Another innovative aspect of the subject matter described in thisdisclosure can be implemented in a client device. The client deviceincludes one or more processors and a memory. The memory storesinstructions that, when executed by the one or more processors, causethe client device to detect a reservation message transmitted by amaster device during a medium reservation window (MRW); determine, basedon the reservation message, a timeslot for which the master device hasreserved access to a shared wireless medium within a medium utilizationperiod (MUP); and schedule communications with the master device overthe shared wireless medium based at least in part on the timeslotreserved by the master device.

In some implementations, execution of the instructions for detecting thereservation message may cause the client device to scan a subset ofchannels allocated for the MRW, wherein the subset of channels is lessthan a number of channels available on the shared wireless medium. Insome implementations, execution of the instructions for schedulingcommunications with the master device may cause the client device tocommunicate with the master device over the shared wireless mediumduring the timeslot reserved by the master device; and operate in apower save state for the remainder of the MUP.

In some aspects, the reservation message may include informationindicating one or more capabilities of the master device. In someimplementations, execution of the instructions may further cause theclient device to associate with the master device based at least in parton the information included in the reservation message.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of an example wireless system.

FIGS. 2A and 2B show timing diagrams depicting example channel accessschemes for a shared wireless medium.

FIGS. 3A and 3B show timing diagrams depicting example channel accessschemes with fixed medium reservation windows.

FIGS. 4A and 4B show timing diagrams depicting example channel accessschemes with variable medium reservation windows.

FIGS. 5A-5C show timing diagrams depicting example operations forsharing a medium access timeslot among multiple master devices.

FIG. 6 shows a block diagram of an example master device.

FIG. 7 shows a block diagram of an example client device.

FIG. 8 shows a flowchart depicting an example operation for reserving awireless medium shared by multiple master devices.

FIG. 9 shows a flowchart depicting an example operation for schedulingaccess to a wireless medium shared by multiple master devices.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

The following description is directed to certain implementations for thepurposes of describing the innovative aspects of this disclosure.However, a person having ordinary skill in the art will readilyrecognize that the teachings herein can be applied in a multitude ofdifferent ways. The described implementations may be implemented in anydevice, system or network that is capable of transmitting and receivingRF signals according to any of the IEEE 16.11 standards, or any of theIEEE 802.11 standards, the Bluetooth® standard, code division multipleaccess (CDMA), frequency division multiple access (FDMA), time divisionmultiple access (TDMA), Global System for Mobile communications (GSM),GSM or General Packet Radio Service (GPRS), Enhanced Data GSMEnvironment (EDGE), Terrestrial Trunked Radio (TETRA), Wideband-CDMA(W-CDMA), Evolution Data Optimized (EV-DO), 1×EV-DO, EV-DO Rev A, EV-DORev B, High Speed Packet Access (HSPA), High Speed Downlink PacketAccess (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved HighSpeed Packet Access (HSPA+), Long Term Evolution (LTE), AMPS, or otherknown signals that are used to communicate within a wireless, cellularor internet of things (IOT) network, such as a system utilizing 3G, 4Gor 5G, or further implementations thereof, technology.

A master device (such as a wireless access point, cellular base station,and the like) may operate on a frequency band shared by other masterdevices in the vicinity. For example, the 6 GHz frequency band may beshared by Wi-Fi and various cellular communication technologies (such asLTE). To avoid interference between different wireless networks andtechnologies, it may be desirable to schedule or otherwise coordinateaccess to the wireless medium among the master devices operating on thesame frequency band. Thus, the implementations described herein mayenable a master device to reserve at least a portion of a shared mediumfor exclusive access by the master device. For example, during theperiod that a master device has reserved access to the shared medium,the master device may service its associated client devices (such asSTAs or user equipment) without interference from neighboring networks.

In some implementations, master devices may contend for access to theshared medium during a medium reservation window (MRW). For example,during the MRW, master devices may advertise their intent to reserve atleast a portion of the shared medium (such as a number of channels orspatial dimensions) for one or more timeslots within a subsequent mediumutilization period (MUP). The reservation messages may be broadcast toall master devices in the vicinity (or on a given channel) to preventother master devices from accessing the wireless medium (or at least aportion thereof) during a reserved timeslot. In some implementations,the owner of a particular timeslot may share at least a portion of itstimeslot with one or more other master devices. For example, the ownerof a particular timeslot may have reserved a greater portion of thewireless medium than needed. Thus, the timeslot owner may enable othermaster devices to utilize the unused portion of the wireless medium(such as unused channels or spatial streams).

Particular implementations of the subject matter described in thisdisclosure can be implemented to realize one or more of the followingpotential advantages. The implementations may reduce interference forwireless devices and networks configured to operate on a sharedfrequency band. For example, by requiring master devices to contend foraccess to the shared medium, aspects of the present disclosure mayensure that each owner of a particular timeslot has exclusive access tothe wireless medium during its allotted timeslot within an MUP.Furthermore, because the reservation messages are broadcast duringscheduled MRWs, on one or more predetermined channels, client devicesmay intercept the reservation messages to determine respective mediumaccess times for each master device in the vicinity. This may allowunassociated client devices to quickly identify all available masterdevices and select a particular master device to associate with. Thisalso may allow associated client devices to enter or remain in a powersaving state when their master devices do not have access to the sharedmedium.

In the following description, numerous specific details are set forthsuch as examples of specific components, circuits, and processes toprovide a thorough understanding of the present disclosure. The term“master device” may refer to any device that provides wireless services(such as a wireless network) to one or more client devices. For example,a master device may correspond to an access point (AP) of a WLAN or abase station (BS) of a cellular network. Thus, the term “client device”may refer to any wireless device that can connect to, or associate with,a master device. For example, a client device may correspond to awireless station (STA) of a WLAN or a user equipment (UE) of a cellularnetwork. The term “associated client device” refers to a client devicethat is already associated with a particular master device, and the term“unassociated client device” refers to a client device that is not yetassociated with any particular master device. In addition, althoughdescribed herein in terms of exchanging data frames between wirelessdevices, the implementations may be applied to the exchange of any dataunit, packet, or frame between wireless devices. Thus, the term “frame”may include any frame, packet, or data unit such as, for example,protocol data units (PDUs), medium access control (MAC) protocol dataunits (MPDUs), aggregated MPDUs (A-MPDUs), and physical layerconvergence procedure protocol data units (PPDUs).

FIG. 1 shows a block diagram of an example wireless system 100. Thewireless system 100 is shown to include two wireless networks 110 and120 in relatively close proximity to one another. The first wirelessnetwork 110 is formed, at least in part, by a first master device (MD)112 that services a number of client devices CD1-CD3. The secondwireless network 120 is formed, at least in part, by a second masterdevice (MD) 122 that services a number of client devices CD4-CD6.Although only two master devices 112 and 122, and six client devicesCD1-CD6, are shown in the example of FIG. 1 for simplicity, it is to beunderstood that the wireless system 100 may include any number of masterdevices or client devices.

The client devices CD1-CD6 may include any suitable wireless deviceincluding, for example, a cell phone, personal digital assistant (PDA),tablet device, laptop computer, or the like. In some implementations,one or more of the client devices CD1-CD6 may be a wireless station(STA) configured to operate in accordance with the IEEE 802.11standards. In some other implementations, one or more of the clientdevices CD1-CD6 may be a user equipment (UE) configured to operate inaccordance with one or more cellular communication standards (such asLong Term Evolution (LTE), Global System for Mobile (GSM), and thelike). Each of the master devices 112 and 122 may be any suitable devicethat allows one or more wireless devices to connect to a network (suchas a local area network (LAN), wide area network (WAN), metropolitanarea network (MAN), a cellular network, or the Internet) using Wi-Fi,Bluetooth, LTE, or any other suitable wireless communication standards.Accordingly, each of the wireless networks 110 and 120 may correspond toa WLAN, cellular (LTE) network, or other wireless communication network.The master devices 112 and 122, and client devices CD1-CD6, may eachinclude one or more transceivers, one or more processing resources (suchas processors or ASICs), one or more memory resources, and a powersource.

In some implementations, the master devices 112 and 122 may beconfigured to operate on a shared wireless medium 101. For example, theshared wireless medium 101 may correspond to the 6 GHz frequency band.Due to the relatively close proximity of the master devices 112 and 122,wireless transmissions within one of the wireless networks 110 or 120may cause interference in the other wireless network. Thus, in someimplementations, the master devices 112 and 122 may schedule orotherwise coordinate access to the shared wireless medium 101 so thatcommunications within the first wireless network 110 do not interferewith communications with the second wireless network 120. In someaspects, each of the master devices 112 and 122 may contend for accessthe shared wireless medium 101.

In some implementations, access to the shared wireless medium may bedivided into a medium reservation window (MRW) followed by a mediumutilization period (MUP). Master devices may contend for access to theshared wireless medium during the MRW, and may service their associatedclient devices during the MUP. Thus, the MRW may be relatively short induration compared to the MUP. In some aspects, the duration of the MRWand the MUP may be fixed. In some other aspects, the duration of the MRWmay vary depending on the number of master devices contending for accessto the shared wireless medium. Still further, in some aspects, theduration of the MUP may vary depending on the channel accessrequirements of the master devices.

During the MRW, master devices may use carrier sense multiple accesscollision avoidance (CSMA/CA) techniques to listen to the wirelessmedium and wait a random back-off period before attempting to transmiton the wireless medium. In some aspects, each of the master devices maylisten to, and contend on, a single common channel of the sharedfrequency band during the MRW. In some other aspects, the master devicesmay contend on different channels of the shared frequency band. A“winning” device (any device that gains access to the wireless mediumduring the MRW) may reserve a timeslot within the following MUP to haveexclusive access to the shared medium. For example, each winning devicemay broadcast a reservation message (RM) advertising the portion of theshared medium it wishes to reserve for the following MUP. In someimplementations, the reservation message may be formatted in a mannerthat can be commonly understood by any master device operating inaccordance with any wireless technology (including Wi-Fi APs andcellular base stations). Further, in some implementations, thereservation message may include a bitmap indicating the timeslot to bereserved for the given master device. For example, the duration of theMUP may be subdivided into 4 ms increments. Thus, each bit of the bitmapmay represent a 4 ms interval within an upcoming MUP.

Within a given timeslot, a master device may reserve the entirety of thefrequency band, a number of channels, a number of spatial streams (ordimensions), or any combination thereof. For example, if a master devicereserves the entirety of the frequency band, no other master devices mayaccess the shared wireless medium during the timeslot reserved for thatmaster device. If a master device reserves only a subset of channelswithin the frequency band, other master devices may access or reservethe unused channels of the shared wireless medium during the timeslotreserved for that master device. If a master device reserves only asubset of spatial streams, other master devices may use or reserve up tothe number of unused spatial streams or dimensions of that master deviceduring its reserved timeslot.

FIG. 2A shows a timing diagram 200A depicting an example channel accessscheme for a shared wireless medium. In the example of FIG. 2A, a numberof master devices MD1-MD3 may compete for access to a shared wirelessmedium (or frequency band). For example, each of the master devicesMD1-MD3 may be located within relatively close proximity of one another(such as within wireless communication range). Each of the masterdevices MD1-MD3 may be an example implementation of master device 112 ormaster device 122 of FIG. 1. For simplicity, only three master devicesMD1-MD3 are shown in the example of FIG. 2A. However, in actualimplementations, there may be any number of master devices sharing thesame wireless medium (or frequency band).

A medium reservation window (MRW) begins at time t₀. During the MRW,from times t₀ to t₃, the master devices MD1-MD3 may contend for accessto the shared wireless medium. In some implementations, each of themaster devices MD1-MD3 may listen to, and contend on, a single commonchannel of the shared frequency band. For example, the first masterdevice MD1 may broadcast a reservation message (RM) upon gaining accessto the shared wireless medium at time t₀. The reservation messagebroadcast by the first master device MD1 may advertise a reservation ofthe shared wireless medium (or at least a number of channels or spatialstreams within the shared wireless medium) for the duration of a firsttimeslot TS1 (from times t₃ to t₄) within a subsequent mediumutilization period (MUP). The other master devices MD2 and MD3 mayreceive the reservation message broadcast by the first master device MD1and refrain from accessing any portion of the shared wireless mediumreserved by the first master device MD1 during the first timeslot TS1.

The second master device MD2 may broadcast a reservation message upongaining access to the shared wireless medium at time t₁. The reservationmessage broadcast by the second master device MD2 may advertise areservation of the shared wireless medium (or at least a number ofchannels or spatial streams within the shared wireless medium) for theduration of a second timeslot TS2 (from times t₄ to t₅) within thesubsequent MUP. The other master devices MD1 and MD3 may receive thereservation message broadcast by the second master device MD2 andrefrain from accessing any portion of the shared wireless mediumreserved by the second master device MD2 during the second timeslot TS2.

The third master device MD3 may broadcast a reservation message upongaining access to the shared wireless medium at time t₂. The reservationmessage broadcast by the third master device MD3 may advertise areservation of the shared wireless medium (or at least a number ofchannels or spatial streams within the shared wireless medium) for theduration of a third timeslot TS3 (from times t₅ to t₆) within thesubsequent MUP. The other master devices MD1 and MD2 may receive thereservation message broadcast by the third master device MD3 and refrainfrom accessing any portion of the shared wireless medium reserved by thethird master device MD3 during the third timeslot TS3.

At the start of the MUP, at time t₃, the first master device MD1 may begranted exclusive access to the shared wireless medium (or at least aportion thereof) for the duration of the first timeslot TS1. During thefirst timeslot TS1, from times t₃ to t₄, the first master device MD1 mayservice its associated client devices (not shown for simplicity) withoutinterference from the remaining master devices MD2 or MD3. Upontermination of the first timeslot TS1, at time t₄, the second masterdevice MD2 may be granted exclusive access to the shared wireless medium(or at least a portion thereof) for the duration of the second timeslotTS2. During the second timeslot TS2, from times t₄ to t₅, the secondmaster device MD2 may service its associated client devices withoutinterference from the remaining master devices MD1 or MD3. Upontermination of the second timeslot TS2, at time t₅, the third masterdevice MD3 may be granted exclusive access to the shared wireless medium(or at least a portion thereof) for the duration of the third timeslotTS3. During the third timeslot TS3, from times t₅ to t₆, the thirdmaster device MD3 may service its associated client devices withoutinterference from the remaining master devices MD1 or MD2. At time t₆,the master devices MD1-MD3 may once again contend for access to theshared wireless medium. Thus, the end of the current MUP (at time t₆)may coincide with the start of another MRW.

In some aspects, client devices also may listen to the common channelassociated with the MRW, from times t₀ to t₃, to intercept thereservation messages broadcast by the master devices MD1-MD3. Forexample, an associated client device may determine the times at whichits master device has access to the shared wireless medium and is thusavailable for wireless communications. Accordingly, the associatedclient device may schedule its power saving states around theavailability of its master device. Furthermore, an unassociated clientdevice may detect the presence of nearby master devices without havingto scan each wireless channel available on the shared wireless medium.For example, only a relatively small subset of the available channelsmay be allocated for each MRW. In some implementations, the reservationmessages may include additional information advertising the capabilitiesof the master devices MD1-MD3. Thus, the unassociated client device mayuse the information provided in the reservation messages (or the signalstrengths of the reservation messages) in selecting a particular masterdevice to associate with.

In some implementations, client devices may be prohibited fromunsolicited access to the wireless medium during the timeslot reservedby its master device. For example, any access to the shared wirelessmedium during a reserved timeslot may be scheduled and provisioned bythe master device that reserved the timeslot. Thus, client devices maynot contend for access to the wireless medium during a reserved timeslotwithin an MUP. In some aspects, a master device may disable any forms ofunscheduled access (such as enhanced distributed channel access (EDCA)or CSMA/CA) to the reserved timeslot within an MUP as long as the masterdevice operates as a collocated BSS. More specifically, as a collocatedBSS, the master device may perform the functions of a BSS in two or morefrequency bands (such as the 2.4, 5, or 6 GHz frequency bands).

For example, a master device may share the 6 GHz frequency band withother master devices, and may thus contend for access to the 6 GHz withother master devices. More specifically, the master device may contendfor access to the 6 GHz frequency band during an MRW and may servicesits client devices over the 6 GHz frequency band during its reservedtimeslot within an MUP. However, if the master device also serves as aBSS in the 2.4 or 5 GHz frequency band, the master device may prohibitits client devices from unscheduled access to the 6 GHz frequency band(specifically, during its reserved timeslot within an MUP) whileallowing the client devices to contend for access to the other frequencybands (such as the 2.4 or 5 GHz frequency band).

FIG. 2B shows a timing diagram 200B depicting another example channelaccess scheme for a shared wireless medium. In the example of FIG. 2B,the master devices MD1-MD3 may compete for access to the shared wirelessmedium (or frequency band) on a per-channel basis. More specifically,each of the master devices MD1-MD3 may compete for individual channelsCH_0-CH_N (or subsets of channels) within the shared frequency band. Forexample, the 6 GHz frequency band may be subdivided into 10-60 channels(depending on regulatory restrictions), each having a bandwidth of 20MHz. Thus, many master devices may be able to service their associatedclient devices using only a subset of the total available bandwidth(such as one or more channels) in the shared frequency band.

An MRW begins at time t₀. During the MRW, from times t₀ to t₂, themaster devices MD1-MD3 may contend for access to the shared wirelessmedium. In the example of FIG. 2B, the first and second master devicesMD1 and MD2 may listen to, and contend on, a first channel CH_0 of theshared frequency band during the MRW. In contrast, the third masterdevice MD3 may listen to, and contend on, a second channel CH_1 of theshared frequency band during the MRW. For example, the first masterdevice MD1 may broadcast a reservation message (RM) upon gaining accessto the first channel CH_0 at time t₀. The reservation message broadcastby the first master device MD1 may advertise a reservation of the firstchannel CH_0 for the duration of a first timeslot TS1 ₀ to (from timest₂ to t₃) within a subsequent medium utilization period (MUP). Thesecond master device MD2 may receive the reservation message broadcastby the first master device MD1 and refrain from accessing the firstchannel CH_0 during the first timeslot TS1 ₀. Since the third masterdevice MD3 is not listening to the first channel CH_0, the third masterdevice MD3 may not receive (or be affected by) the reservation messagebroadcast by the first master device MD1.

The second master device MD2 may broadcast a reservation message upongaining access to the shared wireless medium at time t₁. The reservationmessage broadcast by the second master device MD2 may advertise areservation of the first channel CH_0 for the duration of a secondtimeslot TS2 ₀ (from times t₃ to t₄) within the subsequent MUP. Thefirst master device MD1 may receive the reservation message broadcast bythe first master device MD1 and refrain from accessing the first channelCH_0 during the second timeslot TS2 ₀. Since the third master device MD3is not listening to the first channel CH_0, the third master device MD3also may not receive (or be affected by) the reservation messagebroadcast by the second master device MD2.

Since there are no other master devices contending for access to thesecond channel CH_1, the third master device MD3 may broadcast areservation message upon gaining access to the shared wireless medium attime t₀. It is noted that the first and third master devices MD1 and MD3may broadcast reservation messages at substantially the same time (suchas at time t₀), without interference, because they are operating ondifferent channels. The reservation message broadcast by the thirdmaster device MD3 may advertise a reservation of the second channel CH_1for the duration of a first timeslot TS1 ₁ (from times t₂ to t₄) withinthe subsequent MUP. Since the first and second master devices MD1 andMD2 are not listening to the second channel CH_1, the first and secondmaster devices MD1 and MD2 may not receive (or be affected by) thereservation message broadcast by the third master device MD3.

At the start of the MUP, at time t₂, the first master device MD1 may begranted exclusive access to the first channel CH_0 for the duration ofits corresponding timeslot TS1 ₀, and the third master device MD3 may begranted exclusive access to the second channel CH_1 for the duration ofits corresponding timeslot TS1 ₁. During the first timeslot TS1 ₀ on thefirst channel CH_0, from times t₂ to t₃, the first master device MD1 mayservice its associated client devices (not shown for simplicity) withoutinterference from the remaining master devices MD2 or MD3. Also, duringthe first timeslot TS1 ₁ on the second channel CH_1, from times t₂ tot₄, the third master device MD3 may service its associated clientdevices without interference from the remaining master devices MD1 orMD2. Upon termination of the first timeslot TS1 ₀ on the first channelCH_0, at time t₃, the second master device MD2 may be granted exclusiveaccess to the first channel CH_0 for the duration of its reservedtimeslot TS2 ₀. During the second timeslot TS2 ₀ on the first channelCH_0, from times t₃ to t₄, the second master device MD2 may service itsassociated client device without interference from the remaining masterdevices MD2 or MD3.

At time t₄, the master devices MD1-MD3 may once again contend for accessto the shared wireless medium. Thus, the end of the current MUP (at timet₄) may coincide with the start of another MRW. In some aspects, clientdevices also may listen to one or more of the channels CH_0-CH_N of theshared frequency band, during MRWs, to intercept the reservationmessages broadcast by the master devices MD1-MD3. For example, anassociated client device may listen to the channel(s) on which itsmaster device operates to determine when the master device is availablefor wireless communications. Accordingly, the associated client devicemay schedule its power saving states around the availability of itsmaster device. Furthermore, an unassociated client device may detect thepresence of nearby master devices without having to scan each wirelesschannel available on the shared wireless medium. For example, only arelatively small subset of the available channels (CH_0-CH_N) may beallocated for each MRW. In some implementations, the reservationmessages may include additional information advertising the capabilitiesof the master devices MD1-MD3. Thus, the unassociated client device mayuse the information provided in the reservation message (or the signalstrengths of the reservation messages) in selecting a particular masterdevice to associate with.

In some implementations, client devices may be prohibited fromunsolicited access to the wireless medium during the timeslot reservedby its master device. For example, any access to the shared wirelessmedium during a reserved timeslot may be scheduled by the master devicethat reserved the timeslot. Thus, client devices may not contend foraccess to the wireless medium during a reserved timeslot. In someaspects, a master device may disable any forms of unscheduled access(such as EDCA or CSMA/CA) to the reserved timeslot within an MUP as longas the master device operates as a collocated BSS (and unscheduledaccess is permitted on one of the other frequency bands in which themaster device operates).

FIG. 3A shows a timing diagram 300A depicting an example channel accessscheme with a fixed medium reservation window and a fixed mediumutilization period. In the example of FIG. 3A, a number of masterdevices MD1-MD4 may compete for access to a shared wireless medium (orfrequency band). For example, each of the master devices MD1-MD4 may belocated within relatively close proximity of one another (such as withinwireless communication range). Each of the master devices MD1-MD4 may bean example implementation of master device 112 or master device 122 ofFIG. 1. For simplicity, only four master devices MD1-MD4 are shown inthe example of FIG. 3A. However, in actual implementations, there may beany number of master devices sharing the same wireless medium (orfrequency band).

An MRW begins at time t₀. In some implementations, the MRW may have afixed duration (such as from times t₀ to t₁). However, the duration ofthe MRW may be periodically adjusted based at least in part on thenumber of master devices sharing the wireless medium at a particularinstance of time (such as at certain epochs). During the MRW, from timest₀ to t₁, the master devices MD1-MD4 may contend for access to theshared wireless medium. In some implementations, the master devicesMD1-MD4 may listen to, and contend on, a single common channel of theshared frequency band (such as described with respect to FIG. 2A). Insome other implementations, the master devices MD1-MD4 may contend foraccess to the shared wireless medium on a per-channel basis (such asdescribed with respect to FIG. 2B).

During the MRW, from times t₀ to t₁, the first master device MD1 maybroadcast a reservation message advertising a reservation of the sharedwireless medium for the duration of a first timeslot TS1 (from times t₁to t₂), the second master device MD2 may broadcast a reservation messageadvertising a reservation of the shared wireless medium for the durationof a second timeslot TS2 (from times t₂ to t₃), and the third masterdevice MD3 may broadcast a reservation message advertising a reservationof the shared wireless medium for the duration of a third timeslot TS3(from times t₃ to t₄). In the example of FIG. 3A, the MRW has a fixedduration (such as from times t₀ to t₁) that can accommodate a maximum ofthree reservation messages. Thus, it is noted that the fourth masterdevice does not have time to broadcast a reservation message before theMRW terminates (at time t₁).

At the start of the MUP, at time t₁, the first master device MD1 may begranted exclusive access to the shared wireless medium (or at least aportion thereof) for the duration of the first timeslot TS1. During thefirst timeslot TS1, the first master device MD1 may service itsassociated client devices without interference from the remaining masterdevices MD2-MD4. Upon termination of the first timeslot TS1, at time t₂,the second master device MD2 may be granted exclusive access to theshared wireless medium (or at least a portion thereof) for the durationof the second timeslot TS2. During the second timeslot TS2, the secondmaster device MD2 may service its associated client devices withoutinterference from the remaining master devices MD1, MD3, or MD4. Upontermination of the second timeslot TS2, at time t₃, the third masterdevice MD3 may be granted exclusive access to the shared wireless medium(or at least a portion thereof) for the duration of the third timeslotTS3. During the third timeslot TS3, the third master device MD3 mayservice its associated client devices without interference from theremaining master devices MD1, MD2, or MD4.

A subsequent MRW begins at time t₄. During the subsequent MRW, fromtimes t₄ to t₅, the master devices MD1-MD4 may once again contend foraccess to the shared wireless medium. For example, the fourth masterdevice MD4 may broadcast a reservation message advertising a reservationof the shared wireless medium for the duration of a fourth timeslot TS4(from times t₅ to t₆), the third master device MD3 may broadcast areservation message advertising a reservation of the shared wirelessmedium for the duration of a fifth timeslot TS5 (from times t₆ to t₇),and the first master device MD1 may broadcast a reservation messageadvertising a reservation of the shard wireless medium for the durationof a sixth timeslot TS6 (from times t₇ to t₈). It is noted that, due tothe fixed duration of the MRW (from times t₄ to t₅), the second masterdevice does not have time to broadcast a reservation message before theMRW terminates (at time t₅).

At the start of the next MUP, at time t₅, the fourth master device MD4may be granted exclusive access to the shared wireless medium (or atleast a portion thereof) for the duration of the fourth timeslot TS4.During the fourth timeslot TS4, the fourth master device MD4 may serviceits associated client devices without interference from the remainingmaster devices MD1-MD3. Upon termination of the fourth timeslot TS4, attime t₆, the third master device MD3 may be granted exclusive access tothe shared wireless medium (or at least a portion thereof) for theduration of the fifth timeslot TS5. During the fifth timeslot TS5, thethird master device MD3 may service its associated client deviceswithout interference from the remaining master devices MD1, MD2, or MD4.Upon termination of the fifth timeslot TS5, at time t₇, the first masterdevice MD1 may be granted exclusive access to the shared wireless medium(or at least a portion thereof) for the duration of the sixth timeslotTS6. During the sixth timeslot TS6, the first master device MD1 mayservice its associated client devices without interference from theremaining master devices MD2-MD4.

In the example of FIG. 3A, the MUP also has a fixed duration. Forexample, the duration of the first MUP (from times t₁ to t₄) is equal tothe duration of the second MUP (from times t₅ to t₉). However, themaster devices MD1, MD3, and MD4 may not utilize the entire duration ofthe MUP. For example, the last reserved timeslot TS6 terminates (at timet₈) before the end of the MUP (at time t₉). Thus, there is a period oftime, from times t₈ to t₉, in which the shared wireless medium is leftunutilized. In some implementations, one or more master devices thatwere unable to reserve a timeslot within the given MUP (such as thesecond master device MD2) may access the shared wireless medium duringthe unutilized period. In some aspects, master devices may reserve theshared wireless medium during the unutilized period usingcontention-based channel access techniques (such as CSMA/CA). In someother aspects, the owner of the last timeslot (such as the first masterdevice MD1) may arbitrate access to the wireless medium during theunutilized period.

FIG. 3B shows a timing diagram 300B depicting an example channel accessscheme with a fixed medium reservation window and a variable mediumutilization period. In the example of FIG. 3B, the duration of the MUPmay vary (dynamically) based on the medium access requirements of themaster devices MD1-MD4. More specifically, the MUP may terminate at theend of the last reserved timeslot within the given MUP. Accordingly,there may be no unutilized period within any MUP. In someimplementations, the last master device to reserve a timeslot during acorresponding MRW may broadcast a message indicating when the upcomingMUP is expected to terminate (and when the next MRW is expected tobegin). In some other implementations, each of the master devicesMD1-MD4 may determine the start of the next MRW based on the end of thelast reserved timeslot (such as by monitoring the reservation messagesbroadcast during the MRW).

An MRW begins at time t₀. In some implementations, the MRW may have afixed duration (such as from times t₀ to t₁). However, the duration ofthe MRW may be periodically adjusted based at least in part on thenumber of master devices sharing the wireless medium at a particularinstance of time (such as at certain epochs). During the MRW, from timest₀ to t₁, the master devices MD1-MD4 may contend for access to theshared wireless medium. For example, the first master device MD1 maybroadcast a reservation message advertising a reservation of the sharedwireless medium for the duration of a first timeslot TS1 (from times t₁to t₂), the second master device MD2 may broadcast a reservation messageadvertising a reservation of the shared wireless medium for the durationof a second timeslot TS2 (from times t₂ to t₃), and the third masterdevice MD3 may broadcast a reservation message advertising a reservationof the shared wireless medium for the duration of a third timeslot TS3(from times t₃ to t₄).

In some implementations, the master devices MD1-MD4 may determine thestart of the next MRW based on the reservation messages broadcast duringthe current MRW. For example, the start of the next MRW may coincidewith the end of the last timeslot (TS3) reserved during the current MRW.Thus, in the example of FIG. 3B, the master devices MD1-MD4 maydetermine that the next MRW is expected to begin at time t₄. It is notedthat, due to the fixed duration of the MRW (from times t₀ to t₁) thefourth master device does not have time to broadcast a reservationmessage before the MRW terminates (at time t₁).

At the start of the MUP, at time t₁, the first mater device MD1 may begranted exclusive access to the shared wireless medium (or at least aportion thereof) for the duration of the first timeslot TS1. During thefirst timeslot TS1, the first master device MD1 may service itsassociated client devices without interference from the remaining masterdevices MD2-MD4. Upon termination of the first timeslot TS1, at time t₂,the second master device MD2 may be granted exclusive access to theshared wireless medium (or at least a portion thereof) for the durationof the second timeslot TS2. During the second timeslot TS2, the secondmaster device MD2 may service its associated client devices withoutinterference from the remaining master devices MD1, MD3, or MD4. Upontermination of the second timeslot TS2, at time t₃, the third masterdevice MD3 may be granted exclusive access to the shared wireless medium(or at least a portion thereof) for the duration of the third timeslotTS3. During the third timeslot TS3, the third master device MD3 mayservice its associated client devices without interference from theremaining master devices MD1, MD2, or MD4.

A subsequent MRW begins at time t₄. During the subsequent MRW, fromtimes t₄ to t₅, the master devices MD1-MD4 may once again contend foraccess to the shared wireless medium. For example, the fourth masterdevice MD4 may broadcast a reservation message advertising a reservationof the shared wireless medium for the duration of a fourth timeslot TS4(from times t₅ to t₆), the third master device MD3 may broadcast areservation message advertising a reservation of the shared wirelessmedium for the duration of a fifth timeslot TS5 (from times t₆ to t₇),and the first master device MD1 may broadcast a reservation messageadvertising a reservation of the shard wireless medium for the durationof a sixth timeslot TS6 (from times t₇ to t₈). In some implementations,the master devices MD1-MD4 may determine the start of the next MRW basedon the last timeslot (TS6) reserved during the current MRW. Thus, in theexample of FIG. 3B, the master devices MD1-MD4 may determine that thenext MRW is expected to begin at time t₈. It is noted that, due to thefixed duration of the MRW (from times t₄ to t₅), the second masterdevice does not have time to broadcast a reservation message before theMRW terminates (at time t₅).

At the start of the next MUP, at time t₅, the fourth master device MD4may be granted exclusive access to the shared wireless medium (or atleast a portion thereof) for the duration of the fourth timeslot TS4.During the fourth timeslot TS4, the fourth master device MD4 may serviceits associated client devices without interference from the remainingmaster devices MD1-MD3. Upon termination of the fourth timeslot TS4, attime t₆, the third master device MD3 may be granted exclusive access tothe shared wireless medium (or at least a portion thereof) for theduration of the fifth timeslot TS5. During the fifth timeslot TS5, thethird master device MD3 may service its associated client deviceswithout interference from the remaining master devices MD1, MD2, or MD4.Upon termination of the fifth timeslot TS5, at time t₇, the first masterdevice MD1 may be granted exclusive access to the shared wireless medium(or at least a portion thereof) for the duration of the sixth timeslotTS6. During the sixth timeslot TS6, the first master device MD1 mayservice its associated client devices without interference from theremaining master devices MD2-MD4.

In the example of FIG. 3B, the MUP terminates at the end of the sixthtimeslot TS6 (at time t₈). In comparison with the example channel accessscheme depicted in FIG. 3A, there are no unutilized periods in the MUPof FIG. 3B. Thus, the duration of the MUP may vary based on the mediumaccess requirements of the master devices MD1-MD4. For example, as shownin FIG. 3B, the master devices MD1-MD4 collectively require longeraccess to the shared wireless medium during the first MUP (from times t₁to t₄) than during the second MUP (from times t₅ to t₈). Accordingly,the duration of the second MUP is substantially shorter than theduration of the first MUP.

FIG. 4A shows a timing diagram 400A depicting an example channel accessscheme with a variable medium reservation window and a fixed mediumutilization period. In the example of FIG. 4A, a number of masterdevices MD1-MD4 may compete for access to a shared wireless medium (orfrequency band). For example, each of the master devices MD1-MD4 may belocated within relatively close proximity of one another (such as withinwireless communication range). Each of the master devices MD1-MD4 may bean example implementation of master device 112 or master device 122 ofFIG. 1. For simplicity, only four master devices MD1-MD4 are shown inthe example of FIG. 4A. However, in actual implementations, there may beany number of master devices sharing the same wireless medium (orfrequency band).

An MRW begins at time t₀. During the MRW, the master devices MD1-MD4 maycontend for access to the shared wireless medium. In someimplementations, the master devices MD1-MD4 may listen to, and contendon, a single common channel of the shared frequency band (such asdescribed with respect to FIG. 2A). In some other implementations, themaster devices MD1-MD4 may contend for access to the shared wirelessmedium on a per-channel basis (such as described with respect to FIG.2B). Still further, in some implementations, the duration of the MRW mayvary (dynamically) depending on the number of master devices contendingfor access to the shared wireless medium. For example, the MRW may notterminate until each of the master devices MD1-MD4 has had chance toaccess the shared wireless medium (such as to broadcast a reservationmessage). In some aspects, the MRW may terminate after a period ofinactivity has lapsed.

During the MRW, from times t₀ to t₁, the fourth master device MD4 maybroadcast a reservation message advertising a reservation of the sharedwireless medium for the duration of a first timeslot TS1 (from times t₁to t₂), the third master device MD3 may broadcast a reservation messageadvertising a reservation of the shared wireless medium for the durationof a second timeslot TS2 (from times t₂ to t₃), the first master deviceMD1 may broadcast a reservation message advertising a reservation of theshared wireless medium for the duration of a third timeslot TS3 (fromtimes t₃ to t₄), and the second master device MD2 may broadcast areservation message advertising a reservation of the shared wirelessmedium for the duration of a fourth timeslot TS4 (from times t₄ to t₅).In the example of FIG. 4A, the master devices MD1-MD4 may determine thatthe MRW has terminated when no additional reservations messages havebeen broadcast on the shared wireless medium for at least a thresholdperiod after the reservation message broadcast by the second masterdevice MD2 (such as at time t₁).

At the start of the MUP, at time t₁, the fourth master device MD4 may begranted exclusive access to the shared wireless medium (or at least aportion thereof) for the duration of the first timeslot TS1 (from timest₁ to t₂). Upon termination of the first timeslot TS1, at time t₂, thethird master device MD3 may be granted exclusive access to the sharedwireless medium (or at least a portion thereof) for the duration of thesecond timeslot TS2 (from times t₂ to t₃). Upon termination of thesecond timeslot TS2, at time t₃, the first master device MD1 may begranted exclusive access to the shared wireless medium (or at least aportion thereof) for the duration of the third timeslot TS3 (from timest₃ to t₄). Upon termination of the third timeslot TS3, at time t₄, thesecond master device MD2 may be granted exclusive access to the sharedwireless medium (or at least a portion thereof) for the duration of thefourth timeslot TS4 (from times t₄ to t₅).

A subsequent MRW begins at time t₅. During the subsequent MRW, themaster devices MD1-MD4 may once again contend for access to the sharedwireless medium. For example, the first master device MD1 may broadcasta reservation message advertising a reservation of the shared wirelessmedium for the duration of a fifth timeslot TS5 (from times t₆ to t₇),the second master device MD2 may broadcast a reservation messageadvertising a reservation of the shared wireless medium for the durationof a sixth timeslot TS6 (from times t₇ to t₈), and the third masterdevice MD3 may broadcast a reservation message advertising a reservationof the shared wireless medium for the duration of a seventh timeslot TS7(from times t₈ to t₉).

It is noted that, even though the MRW may be configured to accommodatereservation messages from each of the master devices MD1-MD4, the fourthmaster device MD4 may be unable to reserve any remaining timeslots dueto the fixed duration of the MUP. For example, master devices MD1-MD3have reserved all of the available time in the upcoming MUP. Thus, theduration of the second MRW (from times t₅ to t₆) may be shorter than thefirst MRW (from times t₀ to t₁). In some aspects, the master devicesMD1-MD4 may determine that the MRW has terminated when no additionalreservation messages have been broadcast on the shared wireless mediumfor at least a threshold period after the reservation message broadcastby the third master device MD3 (such as at time t₆).

At the start of the next MUP, at time t₆, the first master device MD1may be granted exclusive access to the shared wireless medium (or atleast a portion thereof) for the duration of the fifth timeslot TS5(from times t₆ to t₇). Upon termination of the fifth timeslot TS5, attime t₇, the second master device MD2 may be granted exclusive access tothe shared wireless medium (or at least a portion thereof) for theduration of the sixth timeslot TS6 (from times t₇ to t₈). Upontermination of the sixth timeslot TS6, at time t₈, the third masterdevice MD3 may be granted exclusive access to the shared wireless medium(or at least a portion thereof) for the duration of the seventh timeslotTS7 (from times t₈ to t₉). In the example of FIG. 4A, the MUP terminatesat the end of the seventh timeslot TS7 (at time t₉), before all of themaster devices MD1-MD4 have had a chance to access the shared wirelessmedium.

FIG. 4B shows a timing diagram 400B depicting an example channel accessscheme with a variable medium reservation window and a variable mediumutilization period. In the example of FIG. 4B, the duration of the MUPmay vary (dynamically) based on the medium access requirements of themaster devices MD1-MD4. More specifically, the MUP may terminate at theend of the last reserved timeslot within the given MUP. In someimplementations, the last master device to reserve a timeslot during acorresponding MRW may broadcast a message indicating when the upcomingMUP is expected to terminate (and when the next MRW is expected tobegin). In some other implementations, each of the master devicesMD1-MD4 may determine the start of the next MRW based on the end of thelast reserved timeslot (such as by monitoring the reservation messagesbroadcast during the MRW).

An MRW begins at time t₀. During the MRW, the master devices MD1-MD4 maycontend for access to the shared wireless medium. In someimplementations, the duration of the MRW may vary (dynamically)depending on the number of mater devices contending for access to theshared wireless medium. In the example of FIG. 4B, the duration of theMRW may be long enough to allow each of the master devices MD1-MD4 toaccess and broadcast a reservation message on the shared wirelessmedium. However, only master devices MD2-MD4 may require access to theshared wireless medium for the upcoming MUP. For example, the firstmaster device MD1 may not have any associated client devices to serviceat this time. In some other implementations, the master devices MD1-MD4may determine that the start of the next MRW is to coincide with the endof the last timeslot (TS3) reserved during the current MRW. Thus, in theexample of FIG. 4B, the master devices MD1-MD4 may determine that thenext MRW is expected to begin at time t₄.

During the MRW, from times t₀ to t₁, the fourth master device MD4 maybroadcast a reservation message advertising a reservation of the sharedwireless medium for the duration of a first timeslot TS1 (from times t₁to t₂), the third master device MD3 may broadcast a reservation messageadvertising a reservation of the shared wireless medium for the durationof a second timeslot TS2 (from times t₂ to t₃), and the second masterdevice MD2 may broadcast a reservation message advertising a reservationof the shared wireless medium for the duration of a third timeslot TS3(from times t₃ to t₄). In the example of FIG. 4B, the master devicesMD1-MD4 may determine that the MRW has terminated when no additionalreservation messages have been broadcast on the shared wireless mediumfor at least a threshold period after the reservation message broadcastby the second master device MD2 (such as at time t₁).

At the start of the MUP, at time t₁, the fourth master device MD4 may begranted exclusive access to the shared wireless medium (or at least aportion thereof) for the duration of the first timeslot TS1 (from timest₁ to t₂). Upon termination of the first timeslot TS1, at time t₂, thethird master device MD3 may be granted exclusive access to the sharedwireless medium (or at least a portion thereof) for the duration of thesecond timeslot TS2 (from times t₂ to t₃). Upon termination of thesecond timeslot TS2, at time t₃, the second master device MD2 may begranted exclusive access to the shared wireless medium (or at least aportion thereof) for the duration of the third timeslot TS3 (from timest₃ to t₄). In the example of FIG. 4B, the MUP terminates at the end ofthe third timeslot TS3 (at time t₄), after each master device requestingaccess to the shared wireless medium (such as master devices MD2-MD4)has had a chance to access the shared wireless medium.

A subsequent MRW begins at time t₄. During the subsequent MRW, themaster devices MD1-MD4 may once again contend for access to the sharedwireless medium. For example, the first master device MD1 may broadcasta reservation message advertising a reservation of the shared wirelessmedium for the duration of a fourth timeslot TS4 (from times t₅ to t₆),the second master device MD2 may broadcast a reservation messageadvertising a reservation of the shared wireless medium for the durationof a fifth timeslot TS5 (from times t₆ to t₇), the third master deviceMD3 may broadcast a reservation message advertising a reservation of theshared wireless medium for the duration of a sixth timeslot TS6 (fromtimes t₇ to t₈), and the fourth master device MD4 may broadcast areservation message advertising a reservation of the shared wirelessmedium for the duration of a seventh timeslot TS7 (from times t₈ to t₉).

It is noted that, at this time, all four of the master devices MD1-MD4may require access to the wireless medium for the upcoming MUP. Thus,the duration of the second MRW (from times t₄ to t₅) may be longer thanthe duration of the first MRW (from times t₀ to t₁). In some aspects,the master devices MD1-MD4 may determine that the MRW has terminatedwhen no additional reservation messages have been broadcast on theshared wireless medium for at least a threshold period after thereservation message broadcast by the fourth master device MD4 (such asat time t₅). In some other aspects, the master devices MD1-MD4 maydetermine the start of the next MRW based on the last timeslot (TS7)reserved during the current MRW. Thus, in the example of FIG. 4B, themaster devices MD1-MD4 may determine that the next MRW is expected tobegin at time t₉.

At the start of the next MUP, at time t₅, the first master device MD1may be granted exclusive access to the shared wireless medium (or atleast a portion thereof) for the duration of the fourth timeslot TS4(from times t₅ to t₆). Upon termination of the fourth timeslot TS4, attime t₆, the second master device MD2 may be granted exclusive access tothe shared wireless medium (or at least a portion thereof) for theduration of the fifth timeslot TS5 (from times t₆ to t₇). Upontermination of the fifth timeslot TS5, at time t₇, the third masterdevice MD3 may be granted exclusive access to the shared wireless medium(or at least a portion thereof) for the duration of the sixth timeslotTS6 (from times t₇ to t₈). Upon termination of the sixth timeslot TS6,at time t₈, the fourth master device MD4 may be granted exclusive accessto the shared wireless medium (or at least a portion thereof) for theduration of the seventh timeslot TS7 (from times t₈ to t₉).

In the example of FIG. 4B, the MUP terminates at the end of the seventhtimeslot TS7 (at time t₉), after each of the master devices MD1-MD4 hashad a chance to access the shared wireless medium. Thus, the duration ofthe MUP may vary based on the medium access requirement of the masterdevices MD1-MD4. For example, as shown in FIG. 4B, the master devicesMD1-MD4 collectively require longer access to the shared wireless mediumduring the second MUP (from times t₅ to t₉) than during the first MUP(from times t₁ to t₄). Accordingly, the duration of the second MUP issubstantially longer than the duration of the first MUP.

FIG. 5A shows a timing diagram 500A depicting an example operation forsharing unused spatial streams (or dimensions) of a shared wirelessmedium during a medium access timeslot. In the example of FIG. 5A, anumber of master devices MD1-MD4 may compete for access to a sharedwireless medium (or frequency band). For example, each of the masterdevices MD1-MD4 may be located within relatively close proximity of oneanother (such as within wireless communication range). Each of themaster devices MD1-MD4 may be an example implementation of master device112 or master device 122 of FIG. 1. For simplicity, only four masterdevices MD1-MD4 are shown in the example of FIG. 5A. However, in actualimplementations, there may be any number of master devices sharing thesame wireless medium (or frequency band).

An MRW begins at time t₀. During the MRW, the master devices MD1-MD4 maycontend for access to the shared wireless medium. For example, the firstmaster device MD1 may broadcast a reservation message advertising areservation of the shared wireless medium for the duration of a firsttimeslot TS1 (from times t₁ to t₂), the second master device MD2 maybroadcast a reservation message advertising a reservation of the sharedwireless medium for the duration of a second timeslot TS2 (from times t₂to t₃), and the third master device MD3 may broadcast a reservationmessage advertising a reservation of the shared wireless medium for theduration of a third timeslot TS3 (from times t₃ to t₄). In the exampleof FIG. 5A, at least one of the MRW or the MUP may have a fixedduration. As a result, the fourth master device MD4 may be unable togain access to the shared wireless medium during the upcoming MUP.

At the start of the MUP, at time t₁, the first master device MD1 may begranted exclusive access to the shared wireless medium for the durationof the first timeslot TS1. During the first timeslot TS1, from times t₁to t₂, the first master device MD1 may service its associated clientdevices without interference from the remaining master devices MD2-MD4.In some implementations, the owner of a timeslot may allow anothermaster device to utilize one or more unused spatial dimensions (orspatial streams) of the shared wireless medium during its reservedtimeslot. For example, two or more master devices may belong to the samemaster device “cluster.” In some implementations, master devicesbelonging to the same cluster may coordinate access to the sharedwireless medium such that two or more master devices may share thewireless medium during a timeslot reserved for only one of the masterdevices in the cluster.

For example, depending on the number of antennas needed to service itsassociated STAs, the first master device MD1 may have a number of unusedspatial dimensions (or spatial streams). In some aspects, the firstmaster device MD1 may use coordinated multipoint (COMP) or Joint MIMOcommunication techniques to share its unused spatial dimensions withanother master device in its cluster (such as the fourth master deviceMD4). For example, the first master device MD1 may use its remainingspatial dimensions to “null” the signals transmitted or received by thefourth master device MD4 so that they do not interfere withcommunications between the first master device MD1 and its associatedclient devices. In the example of FIG. 5A, the first master device MD1may allow the fourth master device MD4 to communicate with itsassociated client devices using up to (but not exceeding) the number ofunused spatial dimensions.

Upon termination of the first timeslot TS1, at time t₂, the secondmaster device MD2 may be granted exclusive access to the shared wirelessmedium (or at least a portion thereof) for the duration of the secondtimeslot TS2. During the second timeslot TS2, from times t₂ to t₃, thesecond master device MD2 may service its associated client deviceswithout interference from the remaining master devices MD1, MD3, or MD4.Upon termination of the second timeslot TS2, at time t₃, the thirdmaster device MD3 may be granted exclusive access to the shared wirelessmedium (or at least a portion thereof) for the duration of the thirdtimeslot TS3. During the third timeslot TS3, from times t₃ to t₄, thethird master device MD3 may service its associated client deviceswithout interference from the remaining master devices MD1, MD2, or MD4.Thus, in the example of FIG. 5A, each of the master devices MD1-MD4 maybe granted access the shared wireless medium even though only threemaster devices MD1-MD3 were able to reserve a timeslot within the MUP.

As described above, the first master device MD1 and fourth master deviceMD4 may belong to the same master device cluster. In someimplementations, master devices that belong to the same cluster may taketurns contending for the shared wireless medium during each MRW. Forexample, because a master device belonging to a master device clustermay share its timeslot with other master devices in the same cluster, itmay be an inefficient allocation of resources to allow multiple masterdevices belonging to the same cluster to reserve individual timeslotswithin an MUP. In some aspects, once a master device belonging to amaster device cluster successfully reserves a timeslot during an MRW,other master devices belonging to the same cluster may subsequentlyrefrain from contending for access to the shared wireless medium duringthat MRW.

In some aspects, client devices that are associated with a master devicebelonging to a master device cluster may schedule their power savingstates based on the availability of any master device belonging to thesame cluster. For example, even though the fourth master device MD4 didnot broadcast a reservation message during the MRW (from times t₀ tot₁), client devices associated with the fourth master device MD4 maynonetheless wake up (or remain awake) during any timeslot allocated foranother master device belonging to the same cluster as the fourth masterdevice MD4 (such as the first master device MD1). Thus, in the exampleof FIG. 5A, client devices associated with the fourth master device MD4may wake up during the first timeslot TS1 (from times t₁ to t₂) with theexpectation that the first master device MD1 could potentially share itsreserved timeslot with the fourth master device MD4.

FIG. 5B shows a timing diagram 500B depicting an example operation forsharing unused channels of a shared wireless medium during a mediumaccess timeslot. In the example of FIG. 5B, each of the master devicesMD1-MD4 may be configured to reserve the shared wireless medium, in itsentirety, for a given duration. For example, each of the master devicesMD1-MD4 may listen to, and contend on, a single common channel of theshared frequency band. Each reservation message broadcast by the masterdevices MD1-MD4 may reserve the entire frequency band for the requestedtimeslot.

An MRW begins at time t₀. During the MRW, the master devices MD1-MD4 maycontend for access to the shared wireless medium. For example, the firstmaster device MD1 may broadcast a reservation message advertising areservation of the shared wireless medium for the duration of a firsttimeslot TS1 (from times t₁ to t₂), the second master device MD2 maybroadcast a reservation message advertising a reservation of the sharedwireless medium for the duration of a second timeslot TS2 (from times t₂to t₃), and the third master device MD3 may broadcast a reservationmessage advertising a reservation of the shared wireless medium for theduration of a third timeslot TS3 (from times t₃ to t₄). In the exampleof FIG. 5B, the fourth master device MD4 may be unable to gain access tothe shared wireless medium during the upcoming MUP (due to the MRW orthe MUP may have a fixed duration).

At the start of the MUP, at time t₁, the first master device MD1 may begranted exclusive access to the shared wireless medium for the durationof the first timeslot TS1. During the first timeslot TS1, from times t₁to t₂, the first master device MD1 may service its associated clientdevices without interference from the remaining master devices MD2-MD4.In some implementations, the owner of a timeslot may allow anothermaster device to utilize one or more unused channels of the sharedwireless medium during its reserved timeslot. For example, while theentirety of the shared frequency band (CH_0-CH_N) may be reserved forthe first master device MD1 during the first timeslot TS1, the firstmaster device MD1 may require only a subset of channels (CH_0) of theshared frequency band to service its associated STAs. Thus, the firstmaster device MD1 may advertise the availability of its unused channels(CH_1-CH_N) during a “quiet period” at the beginning of the firsttimeslot TS1. In some aspects, other master devices may contend foraccess to the unused channels (CH_1-CH_N) using contention-based channelaccess techniques (such as CSM/CA). In some other aspects, the owner ofthe timeslot (such as the first master device MD1) may arbitrate accessto the unused channels (CH_1-CH_N) among the other master devicessharing the wireless medium. Still further, in some aspects, at leastsome of the unused channels may be reserved for onboarding new masterdevices to share the wireless medium (such as for communicatingmanagement information between master devices). In the example of FIG.5B, the first master device MD1 may allow the fourth master device MD4to communicate with its associated client devices during the firsttimeslot TS1 using one or more of the unused channels (CH_1-CH_N).

Upon termination of the first timeslot TS1, at time t₂, the secondmaster device MD2 may be granted exclusive access to the shared wirelessmedium (or at least a portion thereof) for the duration of the secondtimeslot TS2. During the second timeslot TS2, from times t₂ to t₃, thesecond master device MD2 may service its associated client deviceswithout interference from the remaining master devices MD1, MD3, or MD4.Upon termination of the second timeslot TS2, at time t₃, the thirdmaster device MD3 may be granted exclusive access to the shared wirelessmedium (or at least a portion thereof) for the duration of the thirdtimeslot TS3. During the third timeslot TS3, from times t₃ to t₄, thethird master device MD3 may service its associated client deviceswithout interference from the remaining master devices MD1, MD2, or MD4.Thus, in the example of FIG. 5B, each of the master devices MD1-MD4 maybe granted access the shared wireless medium even though only threemaster devices MD1-MD3 were able to reserve a timeslot within the MUP.

FIG. 5C shows a timing diagram 500C depicting an example operation forsharing an unused portion of a reserved timeslot. In someimplementations, the master devices MD1-MD4 may listen to, and contendon, a single common channel of the shared frequency band (such asdescribed with respect to FIG. 2A). In some other implementations, themaster devices MD1-MD4 may contend for access to the shared wirelessmedium on a per-channel basis (such as described with respect to FIG.2B).

An MRW begins at time t₀. During the MRW, the master devices MD1-MD4 maycontend for access to the shared wireless medium. For example, the firstmaster device MD1 may broadcast a reservation message advertising areservation of the shared wireless medium for the duration of a firsttimeslot TS1 (from times t₁ to t₃), the second master device MD2 maybroadcast a reservation message advertising a reservation of the sharedwireless medium for the duration of a second timeslot TS2 (from times t₃to t₄), and the third master device MD3 may broadcast a reservationmessage advertising a reservation of the shared wireless medium for theduration of a third timeslot TS3 (from times t₄ to t₅). In the exampleof FIG. 5C, the fourth master device MD4 may be unable to gain access tothe shared wireless medium during the upcoming MUP (due to the MRW orthe MUP having a fixed duration).

At the start of the MUP, at time t₁, the first master device MD1 may begranted exclusive access to the shared wireless medium for the durationof the first timeslot TS1. During the first timeslot TS1, from times t₁to t₃, the first master device MD1 may service its associated clientdevices without interference from the remaining master devices MD2-MD4.In some implementations, the owner of a timeslot may allow anothermaster device to utilize a portion of unused time during its reservedtimeslot. For example, while the first master device MD1 may havereserved the first timeslot from times t₁ to t₃, the first master deviceMD1 may need only a portion of the reserved time t₀ service itsassociated client devices (from times t₁ to t₂). Thus, the first masterdevice MD1 may advertise the availability of the unused portion of itstimeslot, at time t₂, after servicing its associated client devices. Insome aspects, other master devices may contend for access to thewireless medium during the unused portion of the first timeslot TS1using contention-based channel access techniques (such as CSM/CA). Insome other aspects, the owner of the timeslot (such as the first masterdevice MD1) may arbitrate access to the wireless medium during theunused portion of its timeslot. Still further, in some aspects, at leastsome of the unused portion of the first timeslot TS1 may be reserved foronboarding new master devices to share the wireless medium (such as forcommunicating management information between master devices). In theexample of FIG. 5C, the first master device MD1 may allow the fourthmaster device MD4 to communicate with its associated client devicesduring the unused portion of the first timeslot TS1.

Upon termination of the first timeslot TS1, at time t₃, the secondmaster device MD2 may be granted exclusive access to the shared wirelessmedium (or at least a portion thereof) for the duration of the secondtimeslot TS2. During the second timeslot TS2, from times t₃ to t₄, thesecond master device MD2 may service its associated client deviceswithout interference from the remaining master devices MD1, MD3, or MD4.Upon termination of the second timeslot TS2, at time t₄, the thirdmaster device MD3 may be granted exclusive access to the shared wirelessmedium (or at least a portion thereof) for the duration of the thirdtimeslot TS3. During the third timeslot TS3, from times t₄ to t₅, thethird master device MD3 may service its associated client deviceswithout interference from the remaining master devices MD1, MD2, or MD4.Thus, in the example of FIG. 5C, each of the master devices MD1-MD4 maybe granted access the shared wireless medium even though only threemaster devices MD1-MD3 were able to reserve a timeslot within the MUP.

FIG. 6 shows a block diagram of an example master device 600. Forexample, master device 600 may be an example implementation of any ofthe master devices 112 or 122 of FIG. 1, or master devices MD1-MD3 ofFIGS. 2A and 2B, or master devices MD1-MD4 of FIGS. 3A-5C. The masterdevice 600 may include a PHY 610, a MAC 620, a processor 630, a memory640, and a number of antennas 650(1)-650(n).

The PHY 610 may include a number of transceivers 612 and a basebandprocessor 614. The transceivers 612 may be coupled to the antennas650(1)-650(n), either directly or through an antenna selection circuit(not shown for simplicity). The transceivers 612 may be used tocommunicate wirelessly with one or more client devices, with one or moremaster devices, or with other suitable devices. The baseband processor614 may be used to process signals received from the processor 630 orthe memory 640 and to forward the processed signals to the transceivers612 for transmission via one or more of the antennas 650(1)-650(n), andmay be used to process signals received from one or more of the antennas650(1)-650(n) via the transceivers 612 and to forward the processedsignals to the processor 630 or the memory 640.

Although not shown in FIG. 6, for simplicity, the transceivers 612 mayinclude any number of transmit chains to process and transmit signals toother wireless devices via the antennas 650(1)-650(n), and may includeany number of receive chains to process signals received from theantennas 650(1)-650(n). Thus, in some implementations, the master device600 may be configured for MIMO operations including, for example,single-user MIMO (SU-MIMO) operations and multi-user MIMO (MU-MIMO)operations. In addition, the master device 600 may be configured forOFDMA communications or other suitable multiple access mechanisms, forexample, as may be specified by any of the IEEE 802.11 standards.

The MAC 620 may include at least a number of contention engines 622 andframe formatting circuitry 624. The contention engines 622 may contendfor access to the shared wireless medium, and may store packets fortransmission over the shared wireless medium. In some implementations,the contention engines 622 may be separate from the MAC 620. Stillfurther, in some implementations, the contention engines 622 may beimplemented as one or more software modules (stored in the memory 640 orin memory provided within the MAC 620). The frame formatting circuitry624 may be used to create or format frames received from the processor630 or the memory 640 (such as by adding MAC headers to PDUs provided bythe processor 630), and may be used to re-format frames received fromthe PHY 610 (such as by stripping the MAC headers from frames receivedfrom the PHY 610).

The memory 640 may include a client device (CD) profile data store 641that stores profile information for one or more client devices. Theprofile information for a particular client device may include, forexample, its MAC address, supported data rates, connection history withthe master device 600, one or more resource units (RUs) allocated to theclient device, and any other suitable information pertaining to ordescribing the operation of the client device.

The memory 640 also may include a non-transitory computer-readablemedium (one or more nonvolatile memory elements, such as EPROM, EEPROM,Flash memory, a hard drive, and the like) that may store at least thefollowing software (SW) modules:

-   -   a timeslot (TS) reservation SW module 642 to reserve a shared        wireless medium for a given timeslot within an upcoming medium        utilization period (MUP), the TS reservation SW module 642        including:        -   a medium reservation window (MRW) identification submodule            643 to identify start and end times of MRWs in which to            contend for access to the shared wireless medium; and        -   a coordinated multipoint (COMP) detection submodule 644 to            determine whether another master device belonging to the            same master device cluster has already reserved a timeslot            within the upcoming MUP, and to refrain from contending for            access to the shared wireless medium during the current MRW            upon determining that the other master device already has            the timeslot reserved; and    -   a TS sharing SW module 645 to share at least a portion of the        wireless medium, during the reserved timeslot, with another        master device, the TS sharing SW module 645 including:        -   a channel sharing submodule 646 to advertise an availability            of one or more unused channels during a quiet period at the            beginning of the reserved timeslot;        -   a dimension sharing submodule 647 to share one or more            unused spatial dimensions (or spatial streams) with another            master device belonging to the same master device cluster;            and        -   a time sharing submodule 648 to advertise an availability of            an unused portion (or remaining duration) of the reserved            timeslot after servicing its associated client devices.            Each software module includes instructions that, when            executed by the processor 630, cause the master device 600            to perform the corresponding functions.

For example, the processor 630 may execute the TS reservation SW module642 to reserve a shared wireless medium for a given timeslot within anupcoming MUP. In executing the TS reservation SW module 642, theprocessor 630 may further execute the MRW identification submodule 643or the COMP detection submodule 644. For example, the processor 630 mayexecute the MRW identification submodule 643 to identify start and endtimes of MRWs in which to contend for access to the shared wirelessmedium. The processor 630 also may execute the COMP detection submodule644 to determine whether another master device belonging to the samemaster device cluster has already reserved a timeslot within theupcoming MUP, and to refrain from contending for access to the sharedwireless medium during the current MRW upon determining that the othermaster device already has the timeslot reserved.

The processor 630 may execute the TS sharing SW module 645 to share atleast a portion of the wireless medium, during the reserve timeslot,with another master device. In executing the TS sharing SW module 645,the processor 630 may further execute the channel sharing submodule 646,the dimension sharing submodule 647, or the time sharing submodule 648.For example, the processor 630 may execute the channel sharing submodule646 to advertise an availability of one or more unused channels during aquiet period at the beginning of the reserved timeslot. The processor630 also may execute the dimension sharing submodule 647 to share one ormore unused spatial dimensions (or spatial streams) with another masterdevice belonging to the same master device cluster. Still further, theprocessor 630 may execute the time sharing submodule 648 to advertise anavailability of an unused portion (or remaining duration) of thereserved timeslot after servicing its associated client devices.

FIG. 7 shows a block diagram of an example client device 700. Forexample, client device 700 may be an example implementation of any ofthe client devices CD1-CD6 depicted in FIG. 1. The client device 700 mayinclude a PHY 710, a MAC 720, a processor 730, a memory 740, and anumber of antennas 750(1)-750(n).

The PHY 710 may include a number of transceivers 712 and a basebandprocessor 714. The transceivers 712 may be coupled to the antennas750(1)-750(n), either directly or through an antenna selection circuit(not shown for simplicity). The transceivers 712 may be used tocommunicate wirelessly with one or more master devices, with one or moreclient devices, or with other suitable devices. The baseband processor714 may be used to process signals received from the processor 730 orthe memory 740 and to forward the processed signals to the transceivers712 for transmission via one or more of the antennas 750(1)-750(n), andmay be used to process signals received from one or more of the antennas750(1)-750(n) via the transceivers 712 and to forward the processedsignals to the processor 730 or the memory 740.

Although not shown in FIG. 7, for simplicity, the transceivers 712 mayinclude any number of transmit chains to process and transmit signals toother wireless devices via the antennas 750(1)-750(n), and may includeany number of receive chains to process signals received from theantennas 750(1)-750(n). Thus, in some implementations, the client device700 may be configured for MIMO operations including, for example,single-user MIMO (SU-MIMO) operations and multi-user MIMO (MU-MIMO)operations. In addition, the client device 700 may be configured forOFDMA communications or other suitable multiple access mechanisms, forexample, as may be specified by any of the IEEE 802.11 standards.

The MAC 720 may include at least a number of contention engines 722 andframe formatting circuitry 724. The contention engines 722 may contendfor access to the shared wireless medium, and may store packets fortransmission over the shared wireless medium. In some implementations,the contention engines 722 may be separate from the MAC 720. Stillfurther, in some implementations, the contention engines 722 may beimplemented as one or more software modules (stored in the memory 740 orin memory provided within the MAC 720). The frame formatting circuitry724 may be used to create or format frames received from the processor730 or the memory 740 (such as by adding MAC headers to PDUs provided bythe processor 730), and may be used to re-format frames received fromthe PHY 710 (such as by stripping the MAC headers from frames receivedfrom the PHY 710).

The memory 740 may include a master device (MD) profile data store 741that stores profile information for one or more master devices. Theprofile information for a particular master device may include, forexample, the BSSID, MAC address, channel information, received signalstrength indicator (RSSI) values, goodput values, channel stateinformation (CSI), supported data rates, connection history with themaster device, a trustworthiness value of the master device (indicatinga level of confidence about the master device's location or otherproperties associated with the master device), and any other suitableinformation pertaining to or describing the operation of the masterdevice.

The memory 740 also may include a non-transitory computer-readablemedium (one or more nonvolatile memory elements, such as EPROM, EEPROM,Flash memory, a hard drive, and the like) that may store at least thefollowing software (SW) modules:

-   -   a medium reservation window (MRW) scanning SW module 742 to scan        (or listen to) one or more channels associated with an MRW to        intercept medium reservation messages exchanged by one or more        master devices contending for access to a shared wireless        medium, the MRW sharing SW module 645 including:        -   a master device (MD) detection submodule 743 to identify and            detect one or more capabilities of the master devices based            at least in part on the medium reservation messages            intercepted during the MRW; and        -   an MD association submodule 744 to selectively associate            with one of the master devices based at least in part on the            capabilities detected during the MRW; and    -   a timeslot (TS) detection SW module 745 to identify reserved        timeslots within an upcoming medium utilization period (MUP)        based at least in part on medium reservation messages exchanged        by one or more master devices during an MRW, the TS detection SW        module 745 including:        -   a communication scheduling submodule 746 to schedule            communications with a selected master device, over the            shared wireless medium, during a timeslot reserved by the            selected master device; and        -   a power save scheduling submodule 747 to schedule power save            states for the client device 700 outside of the timeslot            reserved by the selected master device.            Each software module includes instructions that, when            executed by the processor 730, cause the client device 700            to perform the corresponding functions.

For example, the processor 730 may execute the MRW scanning SW module742 to scan (or listen to) one or more channels associated with an MRWto intercept medium reservation messages exchanged by one or more masterdevices contending for access to a shared wireless medium. In executingthe MRW scanning SW module 742, the processor 730 may further executethe MD detection submodule 743 or the MD association submodule 744. Forexample, the processor 730 may execute the MD detection submodule 743 toidentify and detect one or more capabilities of the master devices basedat least in part on the medium reservation messages intercepted duringthe MRW. The processor 730 also may execute the MD association submodule744 to selectively associate with one of the master devices based atleast in part on the capabilities detected during the MRW.

The processor 730 may execute the TS detection SW module 745 to identifyreserved timeslots within an upcoming MUP based at least in part onmedium reservation messages exchanged by one or more master devicesduring an MRW. In executing the TS detection SW module 745, theprocessor 730 may further execute the communication scheduling submodule746 or the power save scheduling submodule 747. For example, theprocessor 730 may execute the communication scheduling submodule 746 toschedule communications with a selected master device, over the sharedwireless medium, during a timeslot reserved by the selected masterdevice. The processor 730 also may execute the power save schedulingsubmodule 747 to schedule power save states for the client device 700outside of the timeslot reserved by the selected master device.

FIG. 8 shows a flowchart depicting an example operation 800 forreserving a wireless medium shared by multiple master devices. Theoperation 800 may be performed by a master device, including any of themaster devices 112 or 122 of FIG. 1, or master devices MD1-MD3 of FIGS.2A and 2B, or master devices MD1-MD4 of FIGS. 3A-5C.

The master device contends with other master devices for access to awireless medium during a medium reservation window (810). In someaspects, the MRW may have a fixed duration. In some other aspects, theduration of the MRW may vary depending on the number of master devicescontending for access to the wireless medium. During the MRW, the masterdevice may use CSMA/CA techniques to listen to the wireless medium andwait a random back-off period before attempting to access or transmit onthe wireless medium. In some implementations, only a relatively smallsubset of the available channels (of the shared frequency band) may beallocated for an MRW. For example, in some aspects, each master devicemay listen to, and contend on, a single common channel during the MRW.In some other aspects, master devices may contend on different channelsof the shared frequency band.

Upon gaining access to the wireless medium during the MRW, the masterdevice may transmit a message to the other master devices advertising areservation of the wireless medium for a timeslot within a mediumutilization period (820). Within a given timeslot, the master device mayreserve the entirety of the frequency band, a subset of channels, asubset of spatial dimensions (or spatial streams), or any combinationthereof. For example, the master device may broadcast a reservationmessage advertising the portion of the shared medium it wishes toreserve for the upcoming MUP. In some implementations, the reservationmessage may be formatted in a manner that can be understood by anymaster device (including Wi-Fi APs and cellular base stations). Further,in some implementations, the reservation message may include a bitmapindicating the timeslot to be reserved for the upcoming MUP. In someaspects, the MUP may have a fixed duration. In some other aspects, theduration of the MUP may vary depending on the channel accessrequirements of the master devices.

The master device may service one or more client devices over thewireless medium during the reserved timeslot within the MUP (830). Forexample, during the reserved timeslot, no other master devices (or theirassociated client devices) may access the shared wireless medium.Accordingly, the master device may service its associated client deviceswith little (or no) interference from other neighboring devices.

In some implementations, the master device may further share at least aportion of the wireless medium, during the reserved timeslot, withanother master device (840). For example, if the master device reservesor uses only a subset of channels of the shared wireless medium, othermaster devices may access or reserve the unused channels during themaster device's timeslot. Similarly, if the master device reserves oruses only a subset of its available spatial streams, other masterdevices (such as master devices belonging to the same master devicecluster) may use or reserve up to the number of unused spatial streamsor dimensions of the master device during its reserved timeslot. Stillfurther, if the master device finishes servicing its client devicesbefore the expiration of its reserved timeslot, other master devices mayuse or access the wireless medium for the remaining portion of themaster device's timeslot.

FIG. 9 shows a flowchart depicting an example operation 900 forscheduling access to a wireless medium shared by multiple masterdevices. The operation 900 may be performed by a client device,including any of the client devices CD1-CD6 of FIG. 1.

The client device may detect a reservation message transmitted by amaster device during a medium reservation window (910). For example, theclient device may scan or listen to the common channel(s) associatedwith the MRW to intercept reservation messages transmitted or broadcastby master devices contending for access to a shared wireless medium. Insome implementations, only a relatively small subset of availablechannels of the shared wireless medium may be allocated for the MRW. Insome aspects, the client device may scan or listen to a single commonchannel associated with the MRW or a particular channel on which anassociated master device is configured to operate. In some otheraspects, client device may scan or listen to each channel associatedwith the MRW to identify and select a master device to associate with.

The client device may determine, based on the reservation message, atimeslot for which the master device has reserved access to a sharedwireless medium within a medium utilization period (920). For example,each reservation message may advertise a timeslot, within the upcomingMUP, that a particular master device wishes to reserve. In someimplementations, the reservation message may include a bitmap indicatingthe timeslot to be reserved for the upcoming MUP. Within a giventimeslot, the master device may reserve the entirety of the frequencyband, a subset of channels, a subset of spatial dimensions (or spatialstreams), or any combination thereof. In some aspects, the client devicemay detect only the timeslot reserved by its associated master device.In some other aspects, the client device may detect the timeslotsreserved by one or more non-associated master devices (such as todetermine the overall duration of the MUP or the start of the next MRW).

The client device may schedule communications with the master deviceover the shared wireless medium based at least in part on the timeslotreserved by the master device (930). For example, during the reservedtimeslot, no other master devices (or their associated client devices)may access the shared wireless medium. Accordingly, the client devicemay communicate with its associated master device with little (or no)interference from other neighboring devices.

In some implementations, the client device may further schedule one ormore power save states based on the reserved timeslot (940). Morespecifically, the client device may schedule its power saving statesaround the available of its associated master device. Since theassociated master device has access to the shared wireless medium onlyduring its reserved timeslot, the client device may operate in a powersave state for any period outside of the timeslot reserved by itsassociated master device (such as the remainder of the MUP).

In some implementations, client devices may be prohibited fromunsolicited access to the wireless medium during the timeslot reservedby its master device. For example, any access to the shared wirelessmedium during a reserved timeslot may be scheduled by the master devicethat reserved the timeslot. Thus, client devices may not contend foraccess to the wireless medium during a reserved timeslot. In someaspects, a master device may disable any forms of unscheduled access(such as EDCA or CSMA/CA) to the reserved timeslot within an MUP as longas the master device operates as a collocated BSS (and unscheduledaccess is permitted on one of the other frequency bands in which themaster device operates).

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover: a, b, c,a-b, a-c, b-c, and a-b-c.

The term “client device,” as used herein, also may refer to as a userequipment (UE), a subscriber station, a mobile unit, a subscriber unit,a wireless unit, a remote unit, a mobile device, a wireless device, awireless communications device, a remote device, a mobile subscriberstation, an access terminal, a mobile terminal, a wireless terminal, aremote terminal, a handset, a user agent, a mobile client, a client, orsome other suitable terminology.

The various illustrative logics, logical blocks, modules, circuits andalgorithm processes described in connection with the implementationsdisclosed herein may be implemented as electronic hardware, computersoftware, or combinations of both. The interchangeability of hardwareand software has been described generally, in terms of functionality,and illustrated in the various illustrative components, blocks, modules,circuits and processes described above. Whether such functionality isimplemented in hardware or software depends upon the particularapplication and design constraints imposed on the overall system.

The hardware and data processing apparatus used to implement the variousillustrative logics, logical blocks, modules and circuits described inconnection with the aspects disclosed herein may be implemented orperformed with a general purpose single- or multi-chip processor, adigital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general purpose processor may be amicroprocessor, or, any conventional processor, controller,microcontroller, or state machine. A processor also may be implementedas a combination of computing devices such as, for example, acombination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration. In some implementations,particular processes and methods may be performed by circuitry that isspecific to a given function.

In one or more aspects, the functions described may be implemented inhardware, digital electronic circuitry, computer software, firmware,including the structures disclosed in this specification and theirstructural equivalents thereof, or in any combination thereof.Implementations of the subject matter described in this specificationalso can be implemented as one or more computer programs, i.e., one ormore modules of computer program instructions, encoded on a computerstorage media for execution by, or to control the operation of, dataprocessing apparatus.

If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. The processes of a method or algorithmdisclosed herein may be implemented in a processor-executable softwaremodule which may reside on a computer-readable medium. Computer-readablemedia includes both computer storage media and communication mediaincluding any medium that can be enabled to transfer a computer programfrom one place to another. A storage media may be any available mediathat may be accessed by a computer. By way of example, and notlimitation, such computer-readable media may include RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that may be used to storedesired program code in the form of instructions or data structures andthat may be accessed by a computer. Also, any connection can be properlytermed a computer-readable medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk, and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above should also be included within the scope ofcomputer-readable media. Additionally, the operations of a method oralgorithm may reside as one or any combination or set of codes andinstructions on a machine readable medium and computer-readable medium,which may be incorporated into a computer program product.

Various modifications to the implementations described in thisdisclosure may be readily apparent to those skilled in the art, and thegeneric principles defined herein may be applied to otherimplementations without departing from the spirit or scope of thisdisclosure. Thus, the claims are not intended to be limited to theimplementations shown herein, but are to be accorded the widest scopeconsistent with this disclosure, the principles and the novel featuresdisclosed herein.

Certain features that are described in this specification in the contextof separate implementations also can be implemented in combination in asingle implementation. Conversely, various features that are describedin the context of a single implementation also can be implemented inmultiple implementations separately or in any suitable subcombination.Moreover, although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Further, the drawings may schematically depict one more exampleprocesses in the form of a flow diagram. However, other operations thatare not depicted can be incorporated in the example processes that areschematically illustrated. For example, one or more additionaloperations can be performed before, after, simultaneously, or betweenany of the illustrated operations. In certain circumstances,multitasking and parallel processing may be advantageous. Moreover, theseparation of various system components in the implementations describedabove should not be understood as requiring such separation in allimplementations, and it should be understood that the described programcomponents and systems can generally be integrated together in a singlesoftware product or packaged into multiple software products.Additionally, other implementations are within the scope of thefollowing claims. In some cases, the actions recited in the claims canbe performed in a different order and still achieve desirable results.

What is claimed is:
 1. A method performed by a master device, comprising: contending with other master devices for access to a wireless medium during a first medium reservation window (MRW); determining a duration of the first MRW based at least in part on a number of master devices contending for access to the wireless medium during the first MRW; upon gaining access to the wireless medium during the first MRW, transmitting a message to the other master devices advertising a reservation of the wireless medium for a timeslot within a first medium utilization period (MUP); and servicing one or more client devices over the wireless medium during the reserved timeslot within the first MUP.
 2. The method of claim 1, wherein each of the master devices comprises a wireless access point or a cellular base station.
 3. The method of claim 1, further comprising: determining an availability of the wireless medium based on reservation messages transmitted by the other master devices during the first MRW; and selecting the timeslot based on the availability of the wireless medium.
 4. The method of claim 1, wherein at least one of the first MRW or the first MUP has a fixed duration.
 5. A method performed by a master device, comprising: contending with other master devices for access to a wireless medium during a first medium reservation window (MRW); upon gaining access to the wireless medium during the first MRW, transmitting a message to the other master devices advertising a reservation of the wireless medium for a timeslot within a first medium utilization period (MUP); determining a duration of the first MUP based at least in part on a medium access requirement of each master device that reserves a timeslot within the first MUP; and servicing one or more devices over the wireless medium during the reserved timeslot within the first MUP.
 6. The method of claim 1, wherein the reservation is for a number of channels, a number of spatial dimensions, a duration of time, or any combination thereof.
 7. The method of claim 1, further comprising: sharing at least a portion of the wireless medium, during the reserved timeslot, with another master device.
 8. The method of claim 7, wherein the shared portion of the wireless medium includes a number of unused channels, a number of unused spatial dimensions, an unused duration of time, or a combination thereof.
 9. The method of claim 8, wherein the sharing comprises: advertising an availability of the shared portion of the wireless medium at the start of the reserved timeslot.
 10. The method of claim 8, wherein the sharing comprises: advertising an availability of the shared portion of the wireless medium after servicing the one or more client devices.
 11. The method of claim 8, wherein the master device and the other master device belong to the same master device cluster.
 12. The method of claim 11, further comprising: determining, during a second MRW, that the other master device has reserved the wireless medium for a timeslot within a second MUP; refraining from contending for access to the wireless medium during the second MRW upon determining that the other master device has reserved the wireless medium; and coordinating access to the wireless medium with the other master device during the timeslot reserved by the other master device within the second MUP.
 13. A master device, comprising: one or more processors; and a memory storing instructions that, when executed by the one or more processors, cause the master device to: contend with other master devices for access to a wireless medium during a first medium reservation window (MRW); upon gaining access to the wireless medium during the first MRW, transmit a message to the other master devices advertising a reservation of the wireless medium for a timeslot within a first medium utilization period (MUP); determine a duration of the first MUP based at least in part on a medium access requirement of each master device that reserves a timeslot within the first MUP; and service one or more client devices over the wireless medium during the reserved timeslot within the first MUP.
 14. The master device of claim 13, wherein execution of the instructions further causes the master device to: determine an availability of the wireless medium based on reservation messages transmitted by the other master devices during the first MRW; and select the timeslot based on the availability of the wireless medium.
 15. The master device of claim 13, wherein at least one of the first MRW or the first MUP has a fixed duration.
 16. A master device, comprising: one or more processors; and a memory storing instructions that, when executed by the one or more processors, cause the master device to: contend with other master devices for access to a wireless medium during a first medium reservation window (MRW); determine a duration of the first MRW based at least in part on a number of master devices contending for access to the wireless medium during the first MRW; upon gaining access to the wireless medium during the first MRW, transmit a message to the other master devices advertising a reservation of the wireless medium for a timeslot within a first medium utilization period (MUP); and service one or more client devices over the wireless medium during the reserved timeslot within the first MUP.
 17. The master device of claim 13, wherein the reservation is for a number of channels, a number of spatial dimensions, a duration of time, or any combination thereof.
 18. The master device of claim 13, wherein execution of the instructions further causes the master device to: share at least a portion of the wireless medium, during the reserved timeslot, with another master device, wherein the shared portion of the wireless medium includes a number of unused channels, a number of unused spatial dimensions, an unused duration of time, or a combination thereof.
 19. The master device of claim 18, wherein the master device and the other master device belong to the same master device cluster.
 20. The master device of claim 19, wherein execution of the instructions further causes the master device to: determine, during a second MRW, that the other master device has reserved the wireless medium for a timeslot within a second MUP; refrain from contending for access to the wireless medium during the second MRW upon determining that the other master device has reserved the wireless medium; and coordinate access to the wireless medium with the other master device during the timeslot reserved by the other master device within the second MUP.
 21. A method performed by a client device, comprising: detecting, during a medium reservation window (MRW), a reservation message transmitted by a master device, wherein the duration of the MRW is based at least in part on a number of master devices contending for access to a shared wireless medium; scanning a subset of channels allocated for the MRW, wherein the subset of channels is less than a number of channels available on the shared wireless medium; determining, based on the reservation message, a timeslot for which the master device has reserved access to the shared wireless medium within a medium utilization period (MUP); and scheduling communications with the master device over the shared wireless medium based at least in part on the timeslot reserved by the master device.
 22. The method of claim 21, wherein the scheduling comprises: communicating with the master device over the shared wireless medium during the timeslot reserved by the master device; and operating in a power save state during the remainder of the MUP.
 23. The method of claim 21, wherein the reservation message includes information indicating one or more capabilities of the master device, the method further comprising: associating with the master device based at least in part on the information included in the reservation message.
 24. A client device, comprising: one or more processors; and a memory storing instructions that, when executed by the one or more processors, cause the client device to: detect a reservation message transmitted by a master device during a medium reservation window (MRW), wherein the duration of the MRW is based at least in part on a number of master devices contending for access to a shared wireless medium; scan a subset of channels allocated for the MRW, wherein the subset of channels is less than a number of channels available on the shared wireless medium; determine, based on the reservation message, a timeslot for which the master device has reserved access to the shared wireless medium within a medium utilization period (MUP); and schedule communications with the master device over the shared wireless medium based at least in part on the timeslot reserved by the master device.
 25. The client device of claim 24, wherein execution of the instructions for scheduling communications with the master device causes the client device to: communicate with the master device over the shared wireless medium during the timeslot reserved by the master device; and operate in a power save state for the remainder of the MUP.
 26. The client device of claim 24, wherein the reservation message includes information indicating one or more capabilities of the master device, and wherein execution of the instructions further causes the client device to: associate with the master device based at least in part on the information included in the reservation message. 